Electro-optical system



Aug. 1, 1939. A. M SKELLETT ELECTRO-OPTICAL SYSTEM Filed Dec. 24/ 1936 AMP . lNl EN TOR AMSKELLETT AT ORNEV- v Pa c e An.

. ammo 7 .arnc'rao-omcar. srs'rm Albert M. Skelleth-MadisonrN. '.I.. assignor to Laboratories,

Bell Telephone Incorporated,

New'ifork, N. Y. a corporation New York Application Deoember 24, 1936. serial No. 111.523

H, scum. (cuts-[20) This invention relates to' electro-opticai sys-- tems and more particularly to the electrographic transmission of-images. a i

In ,copending applicationsof A. M. Skellett, Serial No. 117,521, filed December 4, 1936, and Serial- No. 117,522, filed December 4,1936, there .are disclosed electrographicsystems" for producing imagesirom currents produced. by moving a stylus over ,the subject along selected-paths such as the boundary iinesjbetween distinctiveareas.

The frequency bands required tor the. transmission of these images are small compared with the frequency bands required in ordinary television systems. In the electrographicsystems disclosed in these copending applications, boundaries of distinctive areas or the subject are traced with a v stylus and record members corresponding to the movements of'the stylusmade therefrom. At some later time, which may be very soon there- 20. arisen-signal currents are. generated from these station. There frequently arises asituation where it is desirable to transmit signals as the stylus traces the outlines of the subject. For example,

it may be desired to transmit images of adrawlng as it is taking shape at the transmitting station.

It is an object of this invention to provide an electrographic system having an instantaneous transcriber and converter, that is, one which transmits image currents'corresponding to-the movements oi. a stylus over the boundaries of distinctive areas o! a subject at the same time that the stylus is passing over these boundaries.

In accordance with a preferred embodiment of 38 this invention, shown by way of exampleior purposes of illustration and hereinafter described in' detail, an arrangement is provided for resolving I each point traced by a, stylus or drawing instrumentv in its passage along the boundaries of dis- 40 tinctive areas of a subject, such as agraphic or pictorial representation, into its x'and Y coordinate voltages. Thecoordinate voltages producedare used to control the armatures oi two electromagnets. These armatures have onone 48- end thereof cutting tools which are used to engrave track records on a him. The cutters are mounted on a rotatingstructure, as-is also the iilm, but the cutters rotate at. a slightly higher speed than the him. The relative speeds of the 50 cutters and the iilm are such that the cutters make one complete revolution with respect to the drumuponwhichthe iilmismounted'inoneto twenty minutes, a time which is usually suilicient iortheartisttodrawhissketchortracethe sketch with the stylus. associated-with the mov-z ing, drum and located inside thereof 1 are stationary'photocell pick-ups ior generating at intervals within the period of persistence oi vision image currents which are generated from as much I of the ilhn record as has been engraved up to that z 5 7 time. Currents generated by the photo-cell pickups may be amplified and transmitted to a receiving station and there used to control the production of voltages which are applied across the-de'-' flector plates of, a cathode ray tube to deflect the 10 cathode ray beam therein in accordance with the successive valuesoi the'coordinate voltages. Due to the fact that as much of the representation "as the artist has already traced is retransmitted over and over, each transmission withina time it! interval within the period of persistence of vision,

the observer at .the receiver sees the sketch as it is being drawn. This arrangement is not applicable to the transmission of animated images.

p T The invention will be more readily understood 20 record members-and transmitted'toa'rece'ivlng by referring to the iollowlngfdescription, taken in connection with the accompanying drawing iorming a part thereof; in which:

1 shows an arrangement i'or producing an 80 image oi. a'subiect, suchas a pictorial or graphic representation, while the boundaries of distinctiveareas of this subject are beingv traced at. the transmitting station. In general, the system comprises means such as a stylus ill for tracing the '85 boundaries of distinctive areas of a subject 0,

apparatus for generating two potentials corresponding to thesuccessive positions of the stylus.

, with respect to X and Y coordinate axes, means for recording these coordinate voltages on a 40 record member, and means for immediately transmitting from this record member as much oi the record as has been recorded and repeating this transmission over and over every twentiethoi a second until the whole subjecthas been. aced 4,5

and there is a complete trach record there'oi.'-

Flor producing the two coordinate voltages, a device similar to a telautograph may be used. The stylus It may be connected to two resistances ii and I2 arranged at right angles to each otherso that. as the stylus draws or, traces over the boundaries'oiareas of distinctive tone values 0! the design 0, varying voltages are produced at the resistances which correspond to the X and Y oi the successive positions oi the stylus with respect to a pair of coordinate axes. Connected in circuit with the potentiometer resistances II and I2, respectively, are batteries l3 and 14 which cooperate with the varying resistances H and I2 to produce potentials which vary respectively with the X and Ycoordinates of the successive positions of the stylus point.

After amplification by the amplifiers l6 and I6, the image currents in channels I and 2 are used to ntrol the movement of armatures l1 and ll of ectromagnets l9 and 20-to control the making'of a record of the coordinate voltages as they are generated. Electromagnets l3 and 26 are preferably mounted on a rotating frame member 2|.

Any suitable means such as the brushes 22 and 23 cooperating with slip rings 24 and 26 may be used to make moving contact to the wires leading to the electromagnets i3 and 20. The rotating frame 2| is loosely mounted on a sleeve 26, which sleeve is keyed to the 'shaft2l by any appropriate means such as keys 28 and 29. Frame 2| is adapted to be driven by the shaft 21 (which is in turn driven by the motor '30 through a coupling device 3|) by means of the gear train 32, 33, 34 and 36. The gear 32 is keyed to the shaft 21 by means of key 26 and the gear 36 is fastened to the frame 2| byany suitable means such as the screws 44. The gears 9 32, 33', 34-and 35-have numbers of teeth in such ratio to each other that the frame member'2l makes one complete revolution with respect to the shaft 21 in a period of time which isapproximately from one to twenty minutes, which should be ample time to allowthe artist to completely trace or draw the subject Q. Mounted on the shaft 21 and keyed thereto by means of the key 26 is a rotating drum 36 having a transparent portion-36 upon which a film 31 is mounted.

The film 31 comprisesa film base 33 having a thin opaque layer 40 thereon (see Fig. 2). Armatures I1 and I8 of the electromagnets l3 and 26; have cutter edges 4| whichmove up and down according to'the respective values of the coordinate voltages. In moving up and-down on the surface of the moving film 31 the cutters engrave tracks similarto tracks 42 and 43 of the film 31 shown in Fig. 3. These tracks'are of variable depth and because of the wedge shape of the cutter edge, a path of variable width orarea is engraved in the opaque coating 40 of the film 31.

It will thus be understood that as the stylus lltraces the subject to be transmitted, tracks 42 and 43 will be simultaneously engraved upon a film 31 which corresponds to the variations in the distance of the stylus from the coordinate axes in its successive positions as it traces the boundaries of areas of distinctive tonevalues of the graphic or pictorial representation 0.

Located adjacent the drum 36 is a stationary pick-upmechanism for generating signal current corresponding to the tracks 42 and 43 on the film 31. This pick-up mechanism preferably 'com-' prises a pair of light sources Ill and 6|, darkened partition members 52 and 63 for separating-the two light sources and for confining the light to the 1 desired'optical channels, lenses 64 and 66 which focus the light upon suitable slitapertures 66 and 51 of the supporting member 63 for the partition members 62 and 63 and the restof the optical system located withinthe drum 36, and lenses 66 and 60 which form images of the apertures 66 and 61 upon the film 31 to control the production of photoelectric currents. by the stationary photocell devices 63-and 64. These aperture images are just large enough to cover small areas of the tracks .42 and. 43 of-the film 31. e The tracks 42 and 43 snoop-1a vary the amount of light passing through the filni 31 and this light-of varying intensityis focused by meansof lenses 6| and 62 upon the stationary photocell devices 63 and 64 which generate signal currents corresponding to the potentials generated by means ofthe potentiometer arrangement comprising the resistances .II and I2 and the batteries I3 and I4. ,Q To better'understand the operationof the device in Fig. 1, let it be assumed that the transcriber is drawing or tracing a line'(a boundary of dis- 'tinctive areas) defined by the points I, 2, 3, 4,-etc., of the graphic or pictorial representation in the 64 ata speed of, for example, twenty times a sec- 7 ond,'current will be generated by these cells 63 and 64 every twentieth of a second corresponding to the X and Y coordinates of this pointl. As the Y transcriber progresseswithhis tracinggover the successive points 2, 3, new, the tracks 42 and 43 of the film 31 get progressively longer and every twentieth of a second the image currents generated bythe cells 63.and extend for longer durations of time as theimage currents correspond to a greater number vof points on the boundaries of the subject 0. Inasmuch as the rotating structure 2lis only slightly faster than the drum 36,

the tracks 42 and 43 gradually increase in length, r

the length of these tracks being continually increased until the whole representation 0 has had its boundaries of areas of distinctive tone values traced by the stylus liLf Whenthis finalpoint of the tracing has been reached, the tracks 42 and 43 image currents generated 'every twentieth of a second by the photocells 63 and 64 are in'turn representative of the X and Y coordinates of the successive points of the stylus II) as it traced the boundaries of areas of distinctive tone values of the entire representation 0. With proper timing, the tracks 42 and 43 will extend around the entire circumference of the drum 36 so that there is maximum efficiency in the use of line time. This desirable situation is not'necessary, however, to the operation of the device, as satisfactory pictures are presentedon the fluorescent screen -10 of the cathode ray device H at the receiving stationregardless of whether the entire ien'gth of the film 31 has been used to record the tracks 42 and 43. The method of recording the coordinate voltages, whiie not being claimed as novel per so by the present inventor, offers decidedadvantages for use in this system. The recording is instantane'ous, no development or fixing is required and reproduction may be made from the record any number of times without destroying the. tracks. It is to be understood, however, that this invention is not limited to this specific means of recording, as any-other suitable means possessing these advantages may be-used instead; For example, the potentialsiin channels'l and 2 may beflusedto generate soundsof-the proper frequency and these soundsrecorded on a metal or wax disc, reproduction being made from this disc every twentie'thof a second by vthe usual reproducing devices for this-type of recording.

represent the entire representation 0 and the The signal currents generated by the photo- 16 "i6 thesevariationsiromtherecording carrier waves, it desired, and these waves transmitted to the stationR over suitable line or radio channels Li and L2. Amplifiers 12 g and I! at the tr'ansmitting'station and I4 and II at the receiving station may be used to step up The signals in channels m and L2, after'being received at the receiving station R and amplified 10 by the devices" and 1!, may be aplilliedv two pairs of deflecting plates Ii and-1130i the cathode ray receiving tube II; These potentials when applied to opposite plates of the pairs of sweep plates .16 and 11 cause the beam to be 15 deflected in such a manner that the image on the fluorescent screen corresponds to so much of the representation 0 at the transmitting station as has been traced or drawn up to the particularinstant andcthe observer at the receiving station will thus see the image as it .is being formed. As the signals corresponding to the points previously traced by the; sty1us' III are repeated over and over twenty times a second, a steady image appears on the receiving screen III, which image increases in detail until thewhole representation 1 has been traced. h

The frequency band width required by the system of this invention is relatively small compared with that required in ordinary television systems. It is so small that it is nolarger than those 0! the ordinary high fidelity radio transmitting stations of today. If desired, 'a sound track may provided so that as the observer views the image of the representation 0 taking shape, he may hear the proper sound accompaniment. This system may be very useful in connection with advertising manuiacturers'products. For example, the trade mark 'or distinctivebrand of a manuiacturer's product may have 0 its boundaries of various distinctive tone values huicklytraced by a stylus in the hands of a skilled person at the transmitting station and the impression upon the observer at the receiving; station will be -very effective. This impression should stimulate sales.

I Various modifications may be made in the invention as above disclosed; the'scope of which is indicated by the appended claims. In the claims, the expression boundaries of distinctive areas" is intended, to be inclusive-or. the case 'where a distinctive area is a. line, as in an outline. sketch. The two parallel boundaries of a line area are for practical purposes coincident so that a stylus tracing the line is in eflect' trac- 5 ing e'ach boundary of the line area; that is, tracing both boundaries of the line area simultaneously.' This term, along the boundaries of distinctive areas, is also intended to be inclusive of the case where the areas are distinguishable by so dififerences in elevation as, for example, a figure out from cardboard and placed or mountedupon a fiat support having the same or diflerent tone value or an element of wax forming afield in which aline drawing, figure .or design oi any I .05 kind is produced by indentations in the wax, thus forming depressed line areas; What is'claimedis: l l

l. A method oi image-production the steps of tracing or drawing the boundaries "70 of distinctive areas of a subject, simultaneously generating by said tracing two potentials conentinugu sly' varying in according with the positions 'ofauccessively traced elements or said boundaries recording these potential variations.

smear-1} I g A electric cells 01 and my be used to modulate diately'thereafter, and retransmitting from this --r ecordat intervals within 'the periodof persistence of vision as much otthe; record as has add tracks.

' rate difiere l t tromthat'at which said track been'made u to'that time.

2. In. combination, means for generating two potentials {continuously varying in accordance with suecessive positions of ajstyl'us used to trace the boundaries oi distinctive areas or a subject, means for transmitting image currents corresponding to these ipotentials immediately after said potentials are generated, and means for retransmitting at intervals within the period ;of

persistence oi'vision' as much of the image currents as have been generated up to that time.

V 3. An electrographsystem for the production of an image or a subject while the boundaries 0! distinctive areas-of said subject are being traced bya stylus, comprising means {or generating image currents representative of the location or a portion of one of said boundaries being traced by the stylus with respect to coordinate axes at sub-- stantially thesame time said stylus has traced traced by the. stylus since thetraoing ot'said first portion.

. I 1 7 4- An electro'graph systeml for-the production of an image: of a subject whilethe boundaries of distinctive areas of" said subject are being traced by astyluscomprising means for generat- '.ing'.two'potentials representative'of the location ot-a portion or one of said boundaries belngtraced by the? stylus, with respect-to coordinate axes, apparatus mrecordingv said potentials, means for immediately thereafter transmitting image cur-1 rentsrepresentative o the location or said portion with respect to th coordinate axes from said record member, and means for generating image currents thereafter Fat predetermined intervals within the ofpersistence of vision corresponding to the location of said portion together with the location of such additional portions with respect to* said I coordinate sites as have been traced by the stylus since-the tracing of said first portion.

1 5. In combination, a rotating drum having a.

transparent portion thereof, a film adapted to be fitted over the transparent portion of said drum, said film having an opaque coating on the side remote fromsaid' transparent portion, a rotating member, therate of speed 'of said rotating member with respect to said rotating drum being such that said member makes a complete revolution with respect to the rotating drum in, a rela-- tively long period of time compared with the period oi. time necessary for a complete revolution of either the rotating drum or the rotatingmember,

operated cutters carried by said rotating member, and a stationary photocell pick-up device for generating image currents from 6- In combination; a record member, means. for

moving. said-record member with respect to av vpoint of fixed position, means having movement with respect to said moving record member and al'soxwith respect to'said point oi fixed position to iormatrack on-said record member, and means stationary with respect to saidpoint or died position fol-reading from said track at av stationary means for said moving drum to form tracks on said record 7.. In combination, a drum,-.a record member in the form of a closed band mounted around the periphery of said drum,- means forro'tating said drum, means having movement with respect to said moving drum to form tracks on said record member representative'of electrical signals, and producing electrical signals from said tracks'at a rate diii'erent from that at which said tracks were formed.

8. In combination, a drum, a record member in the form of a closed band mounted around the periphery of said drum, means for rotating said drum, means having movement with respect to member representative of electrical signals, and

stationary means for producing electrical signals from said tracks at a rate different from that at which said tracks were formed, said rotating means and said stationary means cooperating to repeat signals from said record member at periodic intervals.

9. In'combination, a drum, 9. record member in' the form of a closed band of film mounted around the periphery of said drum, said drum having a transparent portion contiguous to said film,

means for rotating said drum, a member carrying electromagnetic cutters, said cutters being so positioned that they contact said film, means for w producing relative movement between the rotating member and said drum whereby tracks are formed on said record member representative of electrical signals which actuate said electromagnetic cutters, and stationary photocell equipment within said drum for producing electrical signals from said track at a rate difierent from that at.

which said tracks were formed, said drum rotating means and said photocell equipment cooper m o repeat signals fromsaid record member at periodic intervals. ALBERT M. SKEILETI. 

